1. Field of the Invention
The present invention is directed to a vacuum sealed subminiature incandescent lamp, and more particularly to a sub-miniature incandescent lamp having an improved filament support wire subassembly.
2. Brief Description of the Prior Art
Subminiature incandescent lamps are well known in the art. Generally speaking such lamps have a diameter of less than approximately 0.5 inch and are frequently used in instrument panels, automotive dash boards and the like. Still further, such lamps are typically designed to work with a power source of approximately 3 to 18 Volts. As is well known in the art, many state-of-the-art lamps include a support wire subassembly the function of which is to mechanically support the incandescent filament, usually in the mid-point between the places of attachment of the filament to the wires or posts which provide electrical contacts to the filament. The support wire subassembly however, generally speaking, does not provide electrical contact or contacts to the filament. As in all incandescent lamps, the interior of the lamp having the support wire subassembly must be sealed from the environment in a gas-tight or vacuum-tight manner. Because hermetically sealing lamps at places where wires or like metal parts extend from the interior of the lamp to the outside has always been a problem in the art (with the art striving to need as few such seals as possible) support wire subassemblies for incandescent lamps are usually kept entirely within the interior of the lamp. One typical state-of-the-art technique to manufacture such lamps is to place a molten glass bead on the base of the electrical contact posts in the interior of the lamp before the lamp is sealed. A molybdenium support wire for the filament is then placed into this glass bead while the bead is still soft enough to embed the wire. After the lamp's envelope is sealed the entire support subassembly is within the interior of the lamp. However, the just described process is expensive because of the extra manufacturing steps involved. Moreover, the entire support wire subassembly including the glass bead is mechanically supported only by the two electric contact wires or posts of the lamp. Therefore, a need exists in the art for a subminiature incandescent lamp with an improved support wire subassembly which is relatively less cumbersome to manufacture. The present invention satisfies this need.